Freeze-in Dirac neutrinogenesis: thermal leptonic CP asymmetry

• Published in: arXiv.org
• Main Authors: Li, Shao-Ping, Li, Xin-Qiang, Yan, Xin-Shuai, Yang, Ya-Dong
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 07.12.2020
• Subjects: Asymmetry; Baryons; Leptons; Neutrinos; Particle decay; Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology; Wave functions
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2005.02927

We present a freeze-in realization of the Dirac neutrinogenesis in which the decaying particle that generates the lepton-number asymmetry is in thermal equilibrium. As the right-handed Dirac neutrinos are produced non-thermally, the lepton-number asymmetry is accumulated and partially converted to the baryon-number asymmetry via the rapid sphaleron transitions. The necessary CP-violating condition can be fulfilled by a purely thermal kinetic phase from the wavefunction correction in the lepton-doublet sector, which has been neglected in most leptogenesis-based setup. Furthermore, this condition necessitates a preferred flavor basis in which both the charged-lepton and neutrino Yukawa matrices are non-diagonal. To protect such a proper Yukawa structure from the basis transformations in flavor space prior to the electroweak gauge symmetry breaking, we can resort to a plethora of model buildings aimed at deciphering the non-trivial Yukawa structures. Interestingly, based on the well-known tri-bimaximal mixing with a minimal correction from the charged-lepton or neutrino sector, we find that a simultaneous explanation of the baryon-number asymmetry in the Universe and the low-energy neutrino oscillation observables can be attributed to the mixing angle and the CP-violating phase introduced in the minimal correction.